Kei Nishikori's bid to go one better at the US Open saw the Japanese fall at the first hurdle, beaten 6-4 3-6 4-6 7-6 (8-6) 6-4 by Frenchman Benoit Paire on Monday.
Nishikori was the beaten finalist against Marin Cilic at Flushing Meadows in 2014, but the world number four became the first major casualty in the men's singles draw of the grand slam after spurning two match points in a fourth-set tie-break.
Paire produced a remarkable recovery to take command in the decider and triumph, which he wrapped up with an ace after three hours, 14 minutes.
Next up for Paire is Marsel Ilhan, who was leading 6-0 2-6 6-4 3-2 when Radek Stepanek retired.
Veteran Mardy Fish prolonged his playing career courtesy of a 6-7 (5-7) 6-3 6-1 6-3 victory over Marco Cecchinato.
The US Open is Fish's final tournament before he retires but the 33-year-old American secured a least one more match against 18th seed Feliciano Lopez.
Lopez defeated qualifier Nikoloz Basilashvili 7-6 (7-5) 6-1 6-3.
World number one Novak Djokovic and defending champion Cilic both emerged from their first-round encounters.
Djokovic - gunning to win his third major of the year - cruised past Joao Souza 6-1 6-1 6-1, while Cilic was less convincing in a 6-3 7-6 (7-3) 7-6 (7-3) victory against qualifier Guido Pella.
Seeds David Ferrer (seventh), Milos Raonic (10th), Grigor Dimitrov (17th) and Jo-Wilfried Tsonga (19th) advanced to the second round on Monday.
Ferrer came from a set down to beat Radu Albot 4-6 7-5 6-1 6-0, Raonic earned his 200th ATP Tour-level win after upstaging Tim Smyczek 6-4 7-6 (10-8) 6-1, Dimitrov cruised to a 6-4 6-2 6-4 win over Matthew Ebden and Tsonga made light work of Jarkko Nieminen 6-3 6-1 6-1.
There were also wins for fellow seeds David Goffin (6-2 6-1 6-1 against Simone Bolelli), Andreas Seppi (6-4 6-0 7-5 over Tommy Paul), Jeremy Chardy (6-2 6-1 6-7 (6-8) 6-2 against Ryan Shane), Roberto Bautista Agut (6-3 6-2 7-6 (9-7) over Pierre-Hugues Herbert) and Tommy Robredo (6-2 6-2 6-4 over Michael Berrer).
French 18th Gael Monfils had no such luck, retiring with Illya Marchenko leading 2-6 6-4 5-0.
Marcel Granollers saw off Lukas Lacko 6-2 6-3 6-1, Fernando Verdasco trumped Tommy Haas 3-6 6-1 6-7 (3-7) 6-3 6-1, Jerzy Janowicz lost 6-3 4-6 6-2 6-4 to Pablo Carreno Busta, Martin Klizan won 6-7 (5-7) 6-3 6-3 3-0 after Florian Mayer retired, while Ricardas Berankis outlasted Joao Sousa 6-2 6-2 4-6 2-6 7-6 (7-4).
Diego Schwartzman accounted for Elias Ymer 6-3 6-2 6-2, Pablo Cuevas defeated Dudi Sela 6-2 3-6 6-4 6-1, Filip Krajinovic blitzed Alejandro Gonzalez 6-4 6-0 6-4, Sergiy Stakhovsky was a 6-1 3-6 7-6 (7-3) 6-4 winner against John Millman and Evgeny Donskoy overcame Lucas Pouille 6-2 6-7 (3-7) 6-2 6-4.
Pablo Andujar's retirement handed Teymuraz Gabashvili victory with their match locked at two sets apiece, Mikhail Kukushkin was leading 6-3 6-3 3-0 when Lu Yen-hsun retired, while Andreas Haider-Maurer posted a 6-4 3-6 6-7 (0-7) 6-0 6-1 win at the expense of a cramping Vasek Pospisil.
